1. Field of the Invention
This invention relates to polyanilines, and more particularly, to polyanilines useful as electrode material, electroconductive material, and circuit element-forming material.
2. Discussion of the Prior Art
Polyaniline has been of great interest as organic electroconductive material and a number of proposals have been made for its application to a variety of fields including batteries, sensors and electrochromic displays. The polyaniline is generally formed by oxidative polymerization of aniline. For application as electronic material, it is desired to form polyaniline from an acidic aqueous solution of aniline by electrolytic or catalytic oxidative polymerization. For oxidative polymerization of aniline, a process of preparing polyaniline by electrolytic oxidation from an acidic aqueous solution of aniline in such an acid as hydrochloric acid, borofluoric acid, sulfuric acid and perchloric acid is known as well as a process of preparing polyaniline by oxidative polymerization from a similar acidic aqueous solution in the presence of such an oxidizing agent as ammonium persulfate, ferric chloride, potassium bichromate, and potassium permanganate.
In order that polyaniline be useful as electronic material, it is particularly important that polyaniline be highly conductive. The polyanilines prepared by the above-mentioned processes are more conductive than those polyanilines prepared from neutral and alkaline solutions, but they are in fact less conductive as compared with conductive inorganic materials such as metals. It is desired to further improve the conductivity of polyaniline.
In order that polyaniline be useful as electronic material, it is also important that the polyaniline bring about no chemical change such as corrosion on an associated material. The polyanilines prepared by the above-mentioned processes cause corrosion of metal materials used therewith because they contain a residue of the acid used in the polymerization step as ammonium salt form. It is proposed to neutralize such polyaniline by treating with an alkali such as ammonia and sodium hydroxide. However, the alkali treatment undesirably reduces conductivity.
In order that polyaniline be useful as electronic material, it is desired to further improve the durability and other properties of polyaniline as electronic material. Particularly when polyaniline is used as electrode material for electrochemical cell, a further improvement in durability and discharge capacity is desired.